Top 17 Helpful Hints for Constructing Electronic Systems

Here's a collection of tips and tricks based on 38 years' experience in the electronics trenches.

I originally wrote this blog for the late, lamented Microcontroller Central. I have updated it with some of the comments and suggestions that it garnered there, along with a few more of my own. Everybody has a favorite idea for making life at work easier. Some of these tips and tricks are handed from old-timers to the younguns. As part of my personal campaign to preserve information, I proudly present the following helpful hints. Some of these ideas are not my own, in which case I have added the name of the person who imparted the technique to me.

Hint No. 1
When I want a cable pair (with no impedance limitations) for a DC power connection or a short communications link, I twist my own using a cordless drill. Simply cut the wire pair (or triplet) to length. Insert one set of ends into the drill chuck, and tighten the chuck, as illustrated below.

The unruly wires are inserted into the drill chuck, and the chuck is tightened. (Click here for a larger image.)

Hold on to the other set of ends, and start the drill. Stop when you have the cable twisted to your desired appearance.

This is so common in my work that I have insisted on having my own drill, so I know the batteries are charged when I need them. If you have any choice in the matter, get a drill with a removable battery, and buy a second battery. (Thank you, Frank Malherbe.)

Hint No. 2
My desk is often a huge jumble of equipment and pieces of electronics, all interconnected. Getting an oscilloscope probe to a particular spot can prove difficult. My answer was to mount my scope on a VDU support arm. This way, it's out of the way until needed. I can then pull it to a convenient spot, connect the probes, and adjust the knobs -- all away from the action on the bench top.

My aging but trusty HP scope mounted on a VDU arm.(Click here for a larger image.)

With the advent of LCD screens, the VDU support arms are more difficult to find nowadays, but they don't need to be quite as sturdy, since modern scopes have shrunken in size and weight. This idea made a surprising reappearance recently in Martin Rowe's column Engineering Data & the Dead Sea Scrolls.

Hint No. 3
It doesn't happen often for microcontroller engineers, but sometimes you need to wind some wire around a toroid. This can be quite frustrating as you try to thread the wire through the hole and extract it on the other side. The solution is to create a bobbin out of plastic or plywood (similar to the figure below) and size it fit through the toroid.

Possible bobbin configuration.

First, you wind the length of wire on to the bobbin. Then you simply thread the bobbin through the toroid, unspooling as you go. (Thank you, Ernesto Gradin.)

Hint No. 4
When I am testing a product, most times I do not have a full system for many practical reasons. This means I have to simulate the real world with switches, potentiometers, and a variety of other doodads. I often need to mount these devices for easy user access. For this, I use a type of material called White Foam PVC.

A simple test aid for a project. Often, with only a few minor modifications, this will become the test jig for production. (Click here for a larger image.)

We buy this as a sheet and cut it to size with a sharp utility knife. It is very easy to make cutouts (also using a knife) or to drill holes.

With the judicious use of a heat shrink gun (or paint heat stripper), it is possible to bend the sheet into a more convenient shape.(Click here for a larger image.)

The result is rigid enough to screw into a wooden base. It doesn't win any prizes for beauty, but it is quick and easy to work. (Thank you, Ernesto Gradin.)

place a small solder reel in through the flap, after first feeding the solder through one of the small holes.

Put some more reels in , you can get two or three reels in depending on size, write the type of solder above the hole, I have typically 311 = very active , 362=general purpose, and X39 low-residual in one caddy, (the other has unleaded and 60/40 1.8%)

All Done! now you have you 3 different solders available with no mess and no tangle, and a handle so you can pick them up. As the caddies are nice rectanglular shaped containers, they can be easily stored away.

Because of the friction inside the caddy, the solder doesn't unspool if you pull sharply on it. And with 3 spools in the caddy it is quite heavy so won't follow you across the bench.

Yep, I wrote a SOP on cutting cable ties using the "cut through the block" method after a helpful employee cut through a soft silicone coolant tube buried deep inside a machine (took 4hrs to replace that tube, after a replacement was airfreighted to him.)

In lieu of twist ties, I prefer to use single conductor wire, e.g. alpha 6715S is hard drawn, no real need to twist once you have wrapped them around the bundle, and you can make S hooks and other shapes that you might otherwise have made with paperclips. Enamelled magnet wire is also good for soft twist ties. Great for getting the loom nice and neat before applying cable ties

n.b. I keep most of my wire under the bench , rolling on something like curtain rod. Under the lip of the bench, about 1" in from the edge, I screw a length of aluminium extrusion (1/8" x 3/4" or whatever ) , it has a strip of self adhesive foam stuck on top (3/8" x 3/4" or thereabouts). The extrusion is screwed enough to half-compress the foam , then you simply push the wire end through the gap between the foam and desk, and the wire stays there after you cut it. You can usually get 3 curtain rods under the average benchtop, so you get a different colored wire every inch or so. So to make a cable of red yellow black green, just grab the four colors you want pull them out to whatever distance, put a quick twist on the loose end (so you can put it in a battery drill as per earlier hint) , cut off the handful of cables, tie a knot at the end just cut, hook that knot over something convenient (the toggle on the bottom of the maggy lamp) and twist it up with a drill.

Note you can get a tighter twist on the cable by one of these methods

give the twisted cable a very strong tug with pliers before releasing the drill chuck

apply a hot air gun gently along the cable before releasing the drill chuck

e.g. You can keep all your jewellers screwdrivers and PCB tools in a neat row stuck to a filing cabinet.

One of the best uses is with small heatshrink, take a bundle of 2 foot lengths of different colors, fold them in the middle, now take a keyring (of the split variety) and feed the bundle in the same way you put a key on the ring, but stop halfway, so the keyring acts like a spring clamp. The steel keyring will stick to any convenient magnet on a filing cabinet maggy lamp etc.

The old style Maggy lamps are almost completely steel, so can be covered with magnets to keep all those small screws etc literally "in your face" .

I tape a magnet to my 4 dioptre "reading" glasses , so it sticks to my maggy lamp. ( Note put the magnet on the left side if your maggy lamp is on the right)

Most crocodile clips, some banana plugs, and all D-types have steel shells, so a lot of test cables will simply stick to magnets.

Well, you must be from America , where "the black wire is always positive" .

I also notice there is a European standard (for wiring of machinery) where all power wiring (220vAC) is red and all DC wiring is black

While on the topic of confusing polarities , Tantalum capacitors have the black stripe on the positive end , and TVS's have the black stripe on the positive terminal (They are zeners after all) . The problem is that Tants, diodes, and TVS's are all available in SMA size packages.

A high-current low-voltage supply can be useful for melting a weak short circuit on an inner PCB layer or other hard-to-access location. I've used a lab supply to do this, but the resistance soldering unit should work great. The voltage has to be low enough so that it doesn't damage anything when (or if) the short opens up.